How should I evaluate and manage an adult with new abdominal pain, watery or bloody diarrhea, and fever after a recent respiratory infection consistent with coronavirus HKU1?

Evaluation and Management of Suspected Coronavirus HKU1 Colitis

Coronavirus HKU1 is rarely the sole cause of gastrointestinal illness, and when detected in stool, it typically represents concurrent respiratory tract infection rather than true colitis. You should focus your evaluation on excluding more common and dangerous causes of bloody diarrhea with fever, particularly bacterial pathogens and Clostridioides difficile.

Initial Clinical Assessment

Obtain a detailed history focusing on:

• Recent antibiotic use within the past month (strongest risk factor for C. difficile) 1
• Recent hospitalization or healthcare exposure 1
• Travel history to endemic areas for enteric pathogens 1
• Common-source food exposures (family gatherings, restaurants) 1
• Timing of respiratory symptoms relative to gastrointestinal symptoms 2
• Characteristics of diarrhea: frequency (episodes per day), presence of blood, duration 2
• Associated symptoms: fever pattern, abdominal pain location and severity, nausea, vomiting 2

Key physical examination findings to document:

• Vital signs including fever ≥38°C (suggests bacterial infection or severe colitis) 3
• Signs of dehydration (orthostatic changes, skin turgor, mucous membranes) 1
• Abdominal examination for peritoneal signs (suggests perforation or severe colitis) 4
• Hepatosplenomegaly (consider typhoid fever if travel history present) 4

Diagnostic Workup

Immediate stool testing should include:

• Rapid C. difficile toxin assay if recent antibiotics or hospitalization 1
• Bacterial stool cultures for Salmonella, Shigella, Campylobacter, and Yersinia 1
• Shiga-toxin-producing E. coli (STEC) testing 1
• Fecal lactoferrin or fecal leukocytes to assess for inflammatory diarrhea 1
• Fecal occult blood testing 1
• Ova and parasite examination with antigen assays for Giardia, Cryptosporidium, Cyclospora, and Entamoeba histolytica if travel exposure 1

Laboratory evaluation:

• Complete blood count (leukocytosis suggests bacterial infection; eosinophilia suggests parasites) 1
• Basic metabolic panel to assess dehydration and electrolyte disturbances 1
• Liver function tests (AST, ALT, bilirubin) - elevated in 15% of COVID-19 patients with GI symptoms 2, 3
• Blood cultures if fever ≥38°C and systemic toxicity 4

Coronavirus testing considerations:

• SARS-CoV-2 testing is reasonable given recent respiratory infection, as diarrhea occurs in 7.7% of COVID-19 patients and may precede respiratory symptoms 2
• Do not perform stool testing for SARS-CoV-2 or other coronaviruses - there is inadequate evidence to support this for diagnosis or monitoring 2, 1
• Coronavirus HKU1 is detected in only 1.3-4.4% of patients with gastrointestinal illness 5, 6
• When HKU1 is found in stool, it is usually detected simultaneously in respiratory samples and often with other established GI pathogens 6, 7

Critical Red Flags Requiring Urgent Intervention

Immediately reassess or hospitalize if:

• Acute worsening of abdominal pain with peritoneal signs (suggests perforation, especially if travel to typhoid-endemic area) 4
• Signs of septic shock or hemodynamic instability 4
• Severe dehydration despite oral rehydration 3
• Markedly elevated leukocyte count (>15,000) 4
• AST:ALT ratio approximately 3:1 (suggests severe liver injury rather than viral gastroenteritis) 3

Management Approach

Supportive care:

• Oral or intravenous rehydration based on severity of dehydration 1
• Electrolyte replacement as indicated by metabolic panel 1
• Avoid loperamide if bloody diarrhea, fever, or suspected invasive bacterial pathogen 8

Empiric antibiotic therapy is NOT recommended until stool culture results return, unless:

• Patient appears septic with high fever and bloody diarrhea
• Travel history to typhoid-endemic area with prolonged fever (>7 days), constipation, and hepatosplenomegaly 4

If stool studies are negative after 48 hours:

• Diarrhea symptoms in COVID-19 are typically self-limited with median duration of 4 days (range 1-9 days) 2
• For persistent diarrhea >14 days with negative initial workup, collect three consecutive stool specimens for parasites 1
• Consider empiric giardiasis treatment if symptoms persist beyond 10-14 days with compatible travel history 1

Follow-up and Monitoring

For patients with elevated liver enzymes:

• Recheck liver function tests in 2-3 weeks 3
• If still elevated, recheck every 1-2 weeks until normalization 3
• Hepatology consultation if liver enzymes worsen or fail to improve after 4-6 weeks 3

Common pitfall to avoid: Do not attribute bloody diarrhea and fever to coronavirus HKU1 infection. While HKU1 can be detected in stool samples, it is found in only 4.4% of patients with GI illness and is usually accompanied by respiratory symptoms and other established GI pathogens 5, 6, 7. The presence of bloody diarrhea strongly suggests a bacterial or inflammatory etiology requiring specific treatment.